GB617339A - An improved method of and means for distilling sea water - Google Patents

Abstract

<PICT:0617339/III/1> In feedwater preheating and distillation systems for steam-driven power plant, particularly marine engines, the feedwater is double or multiple distilled and the condensate from each distillation is condensed by heat exchange with the feed which is thus preheated. Means are provided to prevent the once distilled water from mixing with other feed before it is double distilled. The plant includes arrangements by which part of the feed is only once distilled to provide water for domestic &c. purposes and for condensation of the distillate when no feed is passing to the engines, i.e. when in port. The plant comprises a turbine 2 fed with low-pressure steam through line 1 and provided with an underslung condenser 3, primary evaporators 28 and a secondary evaporator 59, storage tanks 77, 81 for double distilled water, and tanks 64, 66 for single distilled water; feedwater heaters 13, 15, 17 and drain coolers 9, 22, 24, 90, 100 with associated pumps 5, 11, 20, 33, 53. Feedwater for the boilers is provided by condensate from the condenser 3 which is pumped by pumps 5, 11 through air ejector cooler 7, cooler 9 to the preheaters 13, 15, 17 and thence to the boilers through line 18. Sea water, picked up by line 19, is fed by pump 20 through coolers 22, 24, pipes 25, 26 and feed regulator 27 to the evaporators 28 provided with heating coils supplied with exhaust steam from the turbo pump 11 fed through line 37 and also low-pressure steam bled through line 38, reducing valve 39 and pipes 40-43. Debrining ejectors 30 are operated by brine pump 33 and condensate from the coils passes to drain cooler 9. Vapour from the evaporators passes through lines 48, 49 to feed heaters 24, 13, the condensate obtained passing through line 52 to pump 53, a float-controlled valve 55 being provided to maintain levels in heater 13. The pump 53 feeds the condensate to second stage evaporator 59 and the vapours produced are condensed in feed heater 15 and the condensate mixed with condensate obtained from low-pressure steam bled from the turbine through line 45, is fed through lines 72, 73 and cooler 9 as the required make-up for boiler feed. Excess feed may be passed through line 76 to storage tank 77 and thence to tank 81, while excess once-distilled feed is passed through lines 60, 62, 63 to tanks 64, 66. When there is no flow of feed through the preheaters 13, 15, 17, i.e. when the ship is in port, the plant is modified as follows: The evaporators are heated by boiler steam fed through line 84 and the vapours evolved are passed through heat-exchangers 90, 100 cooled by circulation of sea water and the condensate is passed through line 92 to the once distilled storage tanks 64, 66. The second stage evaporator is fed with water drawn from tank 66 through line 94 and is heated by steam supplied through line 96, 68. The vapours pass through lines 29, 98 to cooler 100 and the double distilled condensate is passed through lines 101, 92 to storage tank 77.